1. Field of the Invention
This invention relates to a liquid-transferring hose, more particularly an improved hose for undersea, underwater or floating transfer of liquid, such as oil.
2. Description of the Related Art
When liquid such as oil is delivered by a tanker, liquid is generally loaded or unloaded while the tanker is moored offshore. Liquid such as oil is therefore transferred by a hose line on or under the sea, consisting of a number of hoses connected to each other.
When a hose on or under the sea is damaged, liquid such as oil inside may leak out, possibly leading to pollution of the surroundings and serious social problems.
In order to avoid the above problems, a double-carcass hose is developed. It has a main and auxiliary pressure-resistant cord layers with a liquid-holding buffer layer in-between, which holds liquid leaking out through the main cord layer.
This design allows liquid leaking out through the main pressure-resistant cord layer to be shielded by the auxiliary pressure-resistant cord layer and held in the liquid-holding buffer layer if the main pressure-resistant cord layer is damaged.
This design is extended to a hose which shows an apparently visible external change, when the main pressure-resistant layer is damaged to allow inside liquid to leak out into the liquid-holding buffer layer.
Such a hose is characterized by the auxiliary pressure-resistant cord layer provided with an asymmetrical code layer capable of twisting by pressure of the liquid leaking into the liquid-holding buffer layer, as disclosed by Japanese Patent Application Laid-Open No. 5-272678.
The hose of the above structure, characterized by the auxiliary pressure-resistant cord layer provided with an asymmetrical code layer capable of twisting by pressure of the liquid leaking into the liquid-holding buffer layer, allows an internal damage to be easily discovered by external visual observation, because the asymmetrical cord layer on the auxiliary pressure-resistant layer twists by pressure of the liquid leaking through the main pressure-resistant layer into the liquid-holding buffer layer. Twisting of the asymmetrical cord layer can be easily observed visually, when the outer surface of the hose is marked with a colored straight line or the like.
The above hose, however, could not signal any abnormal appearance, such as twisting of the hose, in the absence of liquid pressure when transfer of liquid under pressure is stopped, even when the conventional hose as described above was provided with an asymmetrical cord layer.
Moreover, it showed little abnormality during the initial stage of liquid leakage, because quantity of leaked liquid was too small to change outer appearance of the hose, and consequently it was impossible to find any abnormality at the initial stage of the liquid leakage.